arm64: head: remove __PHYS_OFFSET

It's very easy to confuse __PHYS_OFFSET and PHYS_OFFSET. To clarify
things, let's remove __PHYS_OFFSET and use KERNEL_START directly, with
comments to show that we're using physical address, as we do for other
objects.

At the same time, update the comment regarding the kernel entry address
to mention __pa(KERNEL_START) rather than __pa(PAGE_OFFSET).

There should be no functional change as a result of this patch.

Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20220629041207.1670133-1-anshuman.khandual@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 6bf685f988f1de4f3af2097909d6d6448c494516..c300b43659dcf0af7638db215c07421fe749a320 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -37,8 +37,6 @@
 
 #include "efi-header.S"
 
-#define __PHYS_OFFSET  KERNEL_START
-
 #if (PAGE_OFFSET & 0x1fffff) != 0
 #error PAGE_OFFSET must be at least 2MB aligned
 #endif
@@ -51,9 +49,6 @@
  *   MMU = off, D-cache = off, I-cache = on or off,
  *   x0 = physical address to the FDT blob.
  *
- * This code is mostly position independent so you call this at
- * __pa(PAGE_OFFSET).
- *
  * Note that the callee-saved registers are used for storing variables
  * that are useful before the MMU is enabled. The allocations are described
  * in the entry routines.
@@ -409,7 +404,7 @@ SYM_FUNC_END(create_kernel_mapping)
 /*
  * The following fragment of code is executed with the MMU enabled.
  *
- *   x0 = __PHYS_OFFSET
+ *   x0 = __pa(KERNEL_START)
  */
 SYM_FUNC_START_LOCAL(__primary_switched)
        adr_l   x4, init_task
@@ -793,7 +788,7 @@ SYM_FUNC_START_LOCAL(__primary_switch)
        adrp    x2, init_idmap_pg_dir
        bl      __enable_mmu
 #ifdef CONFIG_RELOCATABLE
-       adrp    x23, __PHYS_OFFSET
+       adrp    x23, KERNEL_START
        and     x23, x23, MIN_KIMG_ALIGN - 1
 #ifdef CONFIG_RANDOMIZE_BASE
        mov     x0, x22
@@ -815,6 +810,6 @@ SYM_FUNC_START_LOCAL(__primary_switch)
        bl      __relocate_kernel
 #endif
        ldr     x8, =__primary_switched
-       adrp    x0, __PHYS_OFFSET
+       adrp    x0, KERNEL_START                // __pa(KERNEL_START)
        br      x8
 SYM_FUNC_END(__primary_switch)